That is asking a lot of an 80cc saw, especially in hard Aussie wood.
3/8 chain of gauge that's plentiful in your location.
For chains might want a mix of full comp and skip/semi-skip, for when you do thick vs small. I'm a fan of using quality chain with cutter filed ~5-10 degrees.
I like $tihl chain$ but you pay a premium. Those hardwoods semi-chisel might stay sharp longer.
There was a place a few years back , left coast supplies (out of business), that had a wide selection of GB bars at a bargain. The good GB bars are great quality, I should have stocked up. I paid $22 USD for a 25" bar with replaceable tip............if GB is an option check out those.
Concering the saw, if you don't add an aux oiler, put a "waterer" on the bar. Water costs about nothing and heat is the enemy of the bar/chain milling. It will also keep the bar oil on the bar from getting real thin on a hot bar.
Be sure saw is on the rich side of the tune. A MM might let engine heat out better.
People with experience with your sort of trees might have some better suggestions.
If you find you like milling look for a bigger beast for a powerhead.